Harry's copper tube reonator

Hi Dr Pepper,
If you followed the dimensions as I gave them then it should work perfectly. I built several of them for different purposes and never had a problem repeating the results.

As Ivan says, I used copper. You cannot always guarantee what other metals do, so on thing you CAN do is to remove the variable cap so that you only have a metal object.
Drop it into a silver cleaning/plating solution you get from your jewellers shop.

The resultant silver plate to the metal will make a really low resistance surface. If you used copper then this will also increase the Q factor.

One afterthought, are you sure that the tuning capacitor is the correct value?

BR Harry - SM0VPO

Hi,
I do not know for sure, but let me guess.
Steel is almost never used in UHF coaxial devices due to its high resistivity (i.e. losses). Therefore its behaviour is obscure a bit. Steel has much much bigger magnetic permeability than copper or brass. It may influence the properties of the resonator heavily. I personally would avoid using iron or steel here.
Brass is O.K. Polished silver plated brass is used even in top quality devices, if copper is too soft for the purpose.
Various modes of electromagnetic field may exist in a resonator. Check the coupling. Harry supposes use of the basic TEM mode. If a higher mode is excited instead, you can get a 3rd or 5th harmonic or even a non-harmonic frequency response (always on a higher frequency than the basic one).

BR from Ivan OK1SIP

I threw togther the copper tube resonator on Harrys pages.
Harry built it all from copper, I did mine from what I had on hand, a steel outer tube and a brass inner rod, simensions are the same.
Haz says his operates from 100mc to 200mc, but mine operates at 650mc.
Radio waves through steel & brass dont travel at speed difference on an order of 3, so something else is going on here.
Anyone educate me on this please?